Romney helps Ind. Senate candidate in ad

Mitt Romney may have a campaign of his own to run, but he took time out to give a boost to Indiana Senate candidate Richard Mourdock, who faces a tighter-than-expected race.

Romney is featured in a new ad for Mourdock, the Indiana state treasurer who knocked off veteran Sen. Richard Lugar in a GOP primary.

"There is so much at stake," Romney says in the ad, which will begin airing Monday. "Richard will be the 51st vote to repeal and replace government-run health care. Richard will stop the liberal Reid-Pelosi agenda."

That's a subtle dig at Mourdock's opponent, Democratic Rep. Joe Donnelly, who voted for President Obama's health care law. It also ties the Democratic nominee to his party leaders, Harry Reid in the Senate and Nancy Pelosi in the House.

Although Mourdock and his supporters argued that Lugar had been in Washington too long, Lugar had kept the Indiana Senate seat in the GOP column for 36 years. RealClearPolitics considers the Mourdock-Donnelly race a tossup in the GOP-leaning state, and there are reports that Mourdock is tacking to the center to show he can be bipartisan.

Republicans need to hold onto the Indiana seat if they are going to win control of the Senate. Democrats have a 53-47 voting edge, and the Indiana seat would be an unexpected pickup if Donnelly can win.